A large quantity of blast-furnace slag and steel slag are annually produced as industrial byproducts at steel mills. Since efforts to develop the use and application of the byproducts have been insufficient in light of the quantity of production, the byproducts are for the most part reclaimed or left behind in in-house sites. As a result, a serious environmental problem has been raised.
These byproducts are, however, materials that can be sufficiently recycled by proper screening and processing. Particularly, when the blast-furnace slag is used as an alternative to cement among materials for concrete in the construction and building fields, an amount of emission of carbon dioxide generated in the process of producing cement is reduced. The steel slag can replace natural sand as an alternative resource of fine aggregate, so that it can minimize environmental destruction caused by digging sand.
As for the related art, for example, Korean Patent No. 10-0693391 (Patent Document 1) discloses an eco-friendly colorizing concrete composition using steel slag and blast-furnace slag.
Korean Patent No. 10-0694267 (Patent Document 2) discloses marine concrete using steel slag as an aggregate.
Korean Patent No. 10-0451821 (Patent Document 3) discloses a method of increasing an initial strength of concrete using blast-furnace slag cement.
Meanwhile, as a component of a railroad (or railway) track, a sleeper serves to keep the gauge of a track constant, support the train load, and widely distribute the train load to the ballast and roadbed. The sleeper is usually made up of a concrete sleeper body and a fastener for fixing a rail to the concrete body.
Such a sleeper requires a sufficient strength so as to be able to support the train load, and is mainly manufactured with a heavyweight concrete product to effectively secure stability against the track buckling.
Heavyweight concrete products such as railroad (or railway) sleepers have a required strength (a compressive strength of 50 MPa). Since sleepers are exposed to natural environmental factors such as sunlight, snow, rain, varying temperatures, and so on, eco-friendly products are preferable. The heavyweight concrete products such as railroad (or railway) sleepers have not yet been manufactured by adding industrial byproducts such as blast-furnace slag and steel slag.